A well known commercial product in the laundry care industry is the fabric dryer sheet. In use, the consumer typically uses at least one sheet in the drying cycle of the laundering process. The sheets generally include a substrate material, such as a web, wherein the substrate carries one or more ingredients to impart desired benefits to the clothing. These ingredients can include, for example, perfumes, anti-static agents, dye transfer inhibitors, whitening agents, enzymes, stain repellents and wrinkle reducing agents.
Processes for fabricating these dryer sheets are also well known. In a typical process, a large role of the web material is guided at high speeds through various coating, smoothing and drying/cooling steps wherein one or more ingredients are applied to the web. An example of this process is shown in FIG. 1.
With reference to FIG. 1, web 5 is preferably a polyester material and provided in rolls 2. Rolls 2 are typically about 37 inches to about 85 inches in width and have a length between about 8,000 and about 13,000 yards. Web 5 passes through various rollers and rods wherein ingredients are applied to the web. As shown, web 5 is passed over guide roll 12 and onto applicator roll 14. Applicator roll 14 transfers ingredients 17 from coating pan 15 onto the web. A holding tank (not shown) can be used to supply the ingredients to coating pan 15. Preferably, automatic controls are used to ensure a proper level and temperature of ingredients 17 in pan 15.
As known in the art, ingredients 17 can include perfume material in addition to other fabric treatment agents, particularly those that provide anti-static and fabric softening benefits. These fabric treatment agents can include, for example: cationic compounds, such as quarternary ammonium compounds; nonionic surfactants, such as ethoxylated alcohols; fatty alcohols; fatty acids; alkali metal soaps of fatty acids; carboxylic acids and salts thereof; fatty acid esters; glycerides; waxes; anionic surfactants; water; optical brighteners; fluorescent agents; antioxidants; colorants; germacides; perfumes; bacteriocides; enzymes; dye transfer inhibitors; soil release polymers; skin care benefit agents; perfume carriers (e.g. starch, clyclodextrins); wrinkle reducing agents; and the like. Various preferred non-cationic formulations are disclosed in U.S. Pat. No. 6,133,226, filed Apr. 4, 1997, the contents of which is incorporated by reference. In prior art processes, perfume has been present from about 2 wt % to about 6 wt % based on total ingredients 17.
In a preferred embodiment, the ingredients are maintained at approximately 140-190.degree. F. in both the holding tank and coating pan 15. At this temperature, one or more ingredients can be lost to the atmosphere due to their volatility or be adversely affected by means of thermal degradation. When the perfume is present, it is estimated that there is a loss of approximately 15 wt. % of the perfume to the atmosphere at this coating step.
Further on in the process of FIG. 1, after coated in the coating pan, coated web 5' passes over smoothing rod 18 to guide roll 20. From guide roll 20, the web passes to heating drum 22, travels to cooling drums 24 and 26, which are preferably cooled to below about 100.degree. F. by chilled water. Cooled web 5' then passes to trimming station 28, wherein the web is rolled and preferably cut into roles 2'. Roles 2' are preferably about 12 inches in width. At this point in the process, the roles can be stored for later cutting and packaging. During the process shown in FIG. 1, the web can travel as fast as 1,000 feet per minute. It is estimated that the additional perfume lost after the step of coating can be in the range of approximately 20 wt. % to 30 wt. % from that which was originally present in pan 15.
Turning to FIG. 2, final processing of coated web 5' is carried out by passing one or more of the coated roles 2' through a series of guide rollers 32. The web is then folded by folders 34, passed to conveyor 36 and cut by knife 38. After cutting, the folded sheets are tamped down, stacked and accumulated for packaging.
During the above-described processes, it has been found that a significant amount of volatile agents can be lost prior to final packaging, particularly perfumes. This is generally due to the relatively high volatility of most perfume agents. For example, it has been found that up to 45% of the perfume added in a typical process can be lost by the time the dryer sheet is folded and packaged.
Therefore, there is a need for an improved fabric dryer sheet manufacturing process wherein the loss of volatile agents during the process of making the fabric sheets is minimized.
Perfume agents can be classified by their relative volatility. High volatile perfumes are known as "high notes" while relatively unvolatile perfumes are known as "low notes". Due to their high volatility, high note perfumes are typically more perceptible by humans than low note perfumes. High note perfumes also have a wider range of odors and. therefore, allow for greater flexibility when selecting perfume agents. Unfortunately, when manufacturing dryer sheets, it is the desired high notes that can be lost during processing. This has resulted in a decreased amount of high note perfumes making it into the packaged product and alteration of the perfume profile. Use of high note perfumes have also been reduced or eliminated from perfume formulations due to the above-described process conditions.
Therefore, there is also a need for fabric sheet manufacturing techniques that would allow for increased usage of high note perfumes, wherein the highly volatile perfumes are retained on the fabric sheet so as to reach the consumer.